Dilated cardiomyopathy

Next-Generation Cardiac Interfacing Technologies Using Nanomaterial-Based Soft Bioelectronics

Cardiac interfacing devices are essential components for the management of cardiovascular diseases, particularly in terms of electrophysiological monitoring and implementation of therapies. However, conventional cardiac devices are typically composed of rigid and bulky materials and thus pose significant challenges for effective long-term interfacing with the curvilinear surface of a dynamically beating heart. In this regard, the recent development of intrinsically soft bioelectronic devices using nanocomposites, which are fabricated by blending conductive nanofillers in polymeric and elastomeric matrices, has shown great promise. The intrinsically soft bioelectronics not only endure the dynamic beating motion of the heart and maintain stable performance but also enable conformal, reliable, and large-area interfacing with the target cardiac tissue, allowing for high-quality electrophysiological mapping, feedback electrical stimulations, and even mechanical assistance. Here, we explore next-generation cardiac interfacing strategies based on soft bioelectronic devices that utilize elastic conductive nanocomposites. We first discuss the conventional cardiac devices used to manage cardiovascular diseases and explain their undesired limitations. Then, we introduce intrinsically soft polymeric materials and mechanical restraint devices utilizing soft polymeric materials. After the discussion of the fabrication and functionalization of conductive nanomaterials, the introduction of intrinsically soft bioelectronics using nanocomposites and their application to cardiac monitoring and feedback therapy follow. Finally, comments on the future prospects of soft bioelectronics for cardiac interfacing technologies are discussed.

KDM3A knockdown regulates COMP, LOX, COL8A1 and ACOT1 genes in myocardial fibrosis

Cardiovascular disease (CVD) is one of the main causes of death in Saudi Arabia. Cardiac remodeling plays a critical role in the pathophysiology of heart failure. Major focus of our study was to identify crucial genes involved in the pathological remodeling of the heart caused by pressure overload. We utilized various in-silico tools to analyze and interpret microarray data obtained from the Gene Expression Omnibus (GEO) database (GSE120739), including GEO2R analysis, Metascape analysis, WebGestalt analysis, and IPA (Ingenuity pathway analysis). Our findings indicate that certain genes, including Cartilage Oligomeric Matrix Protein (COMP), collagen type VIII alpha 1 chain (COL8A1) and Lysyl Oxidase (LOX) under the influence caused by knockdown of KDM3A, were down regulated by the extracellular matrix pathway. Moreover, genes, such as Acyl-CoA Thioesterase 1 (ACOT1) were up regulated by the fatty acid metabolism pathway. Overexpression of lysine-specific demethylase 3A (KDM3A) leads to the up regulation of fibrosis-related genes COMP, COL8A1, and LOX and the down regulation of ACOT1, result in enhanced fibrosis and heart failure. Our results suggest that COMP, COL8A1, LOX, and ACOT1 warrant further investigation in the development of cardiac fibrosis and as potential biomarkers for causing heart failure.

Effect of dapagliflozin on left ventricular structure and function in patients with non-ischemic dilated cardiomyopathy: An observational study

Non-ischemic dilated cardiomyopathy (NIDCM) is characterized by left ventricular dilatation and contractile dysfunction with severe morbidity and mortality. Sodium glucose cotransporter type 2 (SGLT2) inhibitors significantly reduce cardiovascular events for heart failure patients. We performed to investigate the impact of combined administration of SGLT2 inhibitors on cardiac structure and function in NIDCM patients undergoing conventional therapy. A total of 50 newly diagnosed NIDCM patients received conventional medical therapy, with 23 receiving dapagliflozin 10mg/day in addition (SGLT2i group) and the remaining 27 only receiving conventional therapy (non-SGLT2i group). After 12 months outpatient follow-up, NIDCM patients treated with conventional therapy alone showed a significant reduction of left ventricular end-diastolic dimensions (LVEDd), left ventricular end-systolic dimensions (LVESd), left ventricular end-diastolic volumes (LVEDV), left ventricular end-systolic volumes (LVESV), left ventricular end-diastolic volume index (LVEDVi) and left ventricular end-systolic volume index (LVESVi), while an increase in fractional shortening (FS) and left ventricular ejection fraction (LVEF). Patients receiving dapagliflozin combined with conventional treatment also demonstrated a significant reduction in left ventricular dimensions and volumes, and a marked increase in cardiac function. In non-SGLT2i groups, the % change in LVEDd, LVESd, LVEDV, LVESV, LVEDVi, LVESVi, FS and LVEF was -2.8%, -4.6%, -6.2%, -10.1%, -6.1%, -10.1%, +9.7%, +11%. A greater absolute % fall in left ventricular volume in SGLT2i groups compared to non-SGLT2i groups resulted in a significant improvement in cardiac function. The results showed that SGLT2i combined with conventional therapy has a better beneficial effect on left ventricular volumes and cardiac function in NIDCM patients.

Primate Model Carrying LMNA Mutation Develops Dilated Cardiomyopathy

To solve the clinical transformation dilemma of lamin A/C (LMNA)-mutated dilated cardiomyopathy (LMD), we developed an LMNA-mutated primate model based on the similarity between the phenotype of primates and humans. We screened out patients with LMD and compared the clinical data of LMD with TTN-mutated and mutation-free dilated cardiomyopathy to obtain the unique phenotype. After establishment of the LMNA c.357-2A>G primate model, primates were continuously observed for 48 months, and echocardiographic, electrophysiological, histologic, and transcriptional data were recorded. The LMD primate model was found to highly simulate the phenotype of clinical LMD. In addition, the LMD primate model shared a similar natural history with humans.

Causal Relationship Between Immune Cells/Cytokines and Dilated Cardiomyopathy

To date, whether there is any causal relationship between dilated cardiomyopathy (DCM) and the changes in the levels/expression of immune cells/cytokines is still unclear. This study aimed to investigate the causal relationship between the levels of various types of immune cells/cytokines and DCM. Herein, two-sample Mendelian randomization (MR) (TSMR) using R software was conducted. Single nucleotide polymorphisms (SNPs) related to the levels of various types of immune cells/cytokines and DCM were screened based on the genome-wide association studies (GWAS) obtained from open-source databases. The TSMR was conducted using inverse variance weighted (IVW), method, MR-Egger regression, weighted median method, and simple estimator based on mode to explore the causal association between the levels of each immune cell/cytokine and DCM. Sensitivity analysis was conducted using MR-Egger regression and a leave-one-out sensitivity test. A total of 1816 SNPs related to host immune status and DCM were identified. The IVW results showed a relationship between DCM and the circulating levels of basophils/eosinophils, total eosinophils-basophils, lymphocytes, and C-reactive protein (CRP). Increased lymphocytes levels (odds ratio (OR) = 0.91, 95% confidence interval (CI): 0.84-0.97, P = 0.005) were seen as protective against DCM, whereas increased basophil (OR = 1.18, 95% CI: 1.04-1.33, P = 0.022), eosinophil (OR = 1.1, 95% CI: 1.03-1.17, P = 0.007), eosinophil-basophil (OR = 1.09, 95% CI: 1.02-1.17, P = 0.014), and CRP (OR = 1.1, 95% CI: 1.03-1.18, P = 0.013) levels were associated with an increased risk of DCM. These analyses revealed that there may be a relationship between immune cells/select cytokine status and the onset of DCM. Future studies are required to further validate these outcomes in animal models and clinical trials.

Identification of the Key Genes of Immune Infiltration in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a common cause of heart failure. In this study, we screened the immune infiltration-related genes associated with DCM to explore the potential molecular mechanisms and provide a basis for the early diagnosis and development of new immunotherapeutic targets. A dataset related to DCM was downloaded from the Gene Expression Omnibus (GEO) database. R software was applied to the genetic differential analysis of patients with DCM and healthy individuals, and the obtained differential expressed genes (DEGs) were screened for differentially expressed immune-related genes (DEIRGs) after comparison with the immune microsatellite database. Gene functional analysis established a protein interaction network (PPI). The immune infiltration in patients with DCM versus normal controls was assessed using the CIBERSORT algorithm, the hub genes were screened using the MOCDE app, and the hubs were validated in multiple datasets. A total of 246 DEGs were screened (adj. P < 0.05 and |logFC| > 0.3), and a total of 170 DEIRGs were compared. Gene Ontology analysis showed significant (adj. P < 0.05) Biological Process entries of 591, Cellular Component of 10, and Molecular Function of 39; Kyoto Encyclopedia of Genes and Genomes showed 20 significant entries, mainly focused on cytokines involved in immune-related response, etc. A protein interaction network comprising 28 hub DEGs was constructed in combination with the PPI network interactions. DEIRG was mainly distributed in the T-cell receptor pathway by immune infiltration detection analysis, and significant changes in central memory T-cells were found by analyzing T-cell-related subpathways, where INSR, HLA-B, IFITM1, and HBEGF were significantly differentially expressed. We selected 632 hospitalized patients for validation and found that INSR and HLA-B expression were associated with DCM development by Nomogram. The expression of HLA-B in peripheral blood T-cells was higher in DCM patients than in the normal group, as verified by qRT-PCR. However, the detailed mechanism needs to be further explored.

Genetic characterization of dilated cardiomyopathy patients undergoing heart transplantation in the Chinese population by whole-exome sequencing

BACKGROUND

Dilated cardiomyopathy (DCM) is one of the most frequent causes of heart failure and heart transplantation (HTx). The genetic basis of DCM among patients undergoing HTx remains to be further studied. This study aimed to characterize the genetic basis of DCM HTx in the Chinese population.

METHODS

In total, 208 unrelated DCM patients who underwent HTx at Fuwai Hospital between June 2004 and June 2017 were included in this study. Whole-exome sequencing (WES) was performed for all patients. Gene burden analysis, variant classification, and genotype-phenotype correlation analysis were subsequently performed.

RESULTS

After completing the bioinformatics analysis, gene burden analysis suggested that titin (TTN), filamin C (FLNC) and lamin A/C (LMNA) were significantly enriched with rare protein-altering variants. The frequencies of TTN and FLNC truncating variants in our cohort were 18.8% and 8.7%, respectively. Among the 165 rare variants in high evidence DCM-related genes, 27 (16.4%) and 59 (35.8%) were interpreted as pathogenic (P) and likely pathogenic (LP), respectively. In addition, 41 (47.7%) and 16 (18.6%) of these 86 P/LP variants are located in TTN and FLNC, respectively. The FLNC group contained more patients with NYHA class IV than the P/LP-negative group (FLNC, 16/18 vs. P/LP-negative, 81/123, P = 0.049).

CONCLUSIONS

Based on WES, we provided a primary genetic spectrum of DCM patients undergoing HTx in the Chinese population. TTN and FLNC harbour the most P/LP variants. FLNC truncation may lead to severe clinical symptoms in DCM patients.

The genetic basis for adult-onset idiopathic dilated cardiomyopathy in people of African descent

Cardiomyopathies are a heterogeneous group of cardiac muscle disorders that result in dilated, hypertrophic, or restrictive pathophysiological entities. Dilated cardiomyopathy (DCM) is the most common form in sub-Saharan Africa (SSA). However, population-specific research studies reporting the actual burden of DCM in this region are still lacking. Also, little is known about the genetic basis of DCM in this population, and genetic testing is still not readily accessible. This review describes the common pathogenic genes implicated in DCM globally and discusses the evidence-based management of patients with DCM. We also present a summary of studies describing genes implicated or associated with DCM in patients residing in SSA.

Development of Dilated Cardiomyopathy in a Young Woman After Bilateral Cardiac Sympathetic Denervation in Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) can cause fatal tachyarrhythmias brought on by physical or emotional stress. Previously published cases deny the association between CPVT with dilated cardiomyopathy (DCM). However, rare cases show a possible association between CPVT and DCM development. Our case is one of them; we describe the development of dilated cardiomyopathy in a young woman who, six years earlier, went through bilateral cardiac sympathetic denervation (CSD) because of symptomatic catecholaminergic polymorphic ventricular tachycardia.

Determining the Likelihood of Disease Pathogenicity Among Incidentally Identified Genetic Variants in Rare Dilated Cardiomyopathy-Associated Genes

Background As utilization of clinical exome sequencing (ES) has expanded, criteria for evaluating the diagnostic weight of incidentally identified variants are critical to guide clinicians and researchers. This is particularly important in genes associated with dilated cardiomyopathy (DCM), which can cause heart failure and sudden death. We sought to compare the frequency and distribution of incidentally identified variants in DCM-associated genes between a clinical referral cohort with those in control and known case cohorts to determine the likelihood of pathogenicity among those undergoing genetic testing for non-DCM indications. Methods and Results A total of 39 rare, non-TTN DCM-associated genes were identified and evaluated from a clinical ES testing referral cohort (n=14 005, Baylor Genetic Laboratories) and compared with a DCM case cohort (n=9442) as well as a control cohort of population variants (n=141 456) derived from the gnomAD database. Variant frequencies in each cohort were compared. Signal-to-noise ratios were calculated comparing the DCM and ES cohort with the gnomAD cohort. The likely pathogenic/pathogenic variant yield in the DCM cohort (8.2%) was significantly higher than in the ES cohort (1.9%). Based on signal-to-noise and correlation analysis, incidental variants found in FLNC, RBM20, MYH6, DSP, ABCC9, JPH2, and NEXN had the greatest chance of being DCM-associated. Conclusions The distribution of pathogenic variants between the ES cohort and the DCM case cohort was gene specific, and variants found in the ES cohort were similar to variants found in the control cohort. Incidentally identified variants in specific genes are more associated with DCM than others.

Elevated α-hydroxybutyrate dehydrogenase is associated with in-hospital mortality in non-ischemic dilated cardiomyopathy

Background

Previous Study Found That Implantation of a Cardioverter-Defibrillator Likely Caused a Worse Prognosis in Older Patients With non-Ischemic Systolic Heart Failure. This Suggests That More Precise Risk Stratification Is Needed in Elderly Patients. We Conducted a Retrospective Study to Evaluate the Association of α-Hydroxybutyrate Dehydrogenase (α-HBDH) With Mortality During Hospitalization in Elderly Patients With non-Ischemic Dilated Cardiomyopathy (NIDCM).

Methods

1,019 Elderly Patients (age ≥60 Years) Diagnosed With NIDCM Were Retrospectively Enrolled From January 2010 to December 2019. Univariate and Multivariate Analyses Were Showed to Explore the Relationship Between α-HBDH and in- Hospital Death.

Results

Patients in elevated α-HBDH group (>182 U/L) had a longer hospital stays and higher in-hospital mortality. Univariate logistics regression analysis showed that elevated α-HBDH was significantly related to mortality (OR: 7.004, 95% CI: 3.583–13.693, p < 0.001). Receiver operator characteristic (ROC) curve analysis reflected that α-HBDH levels had excellent predictive power for in-hospital death (AUC = 0.810, 95% CI: 0.745–0.876, p < 0.001). After adjustment of age, serum creatine, albumin and LVEF, multivariate regression analysis validated the association of elevated α-HBDH with increased risk of in-hospital death (p < 0.05).

Conclusions

Elevated α-HBDH level is significantly related to in-hospital mortality in older patients with NIDCM.

Arrhythmogenic Cardiomyopathy: Exercise Pitfalls, Role of Connexin-43, and Moving beyond Antiarrhythmics

Arrhythmogenic Cardiomyopathy (ACM), a Mendelian disorder that can affect both left and right ventricles, is most often associated with pathogenic desmosomal variants that can lead to fibrofatty replacement of the myocardium, a pathological hallmark of this disease. Current therapies are aimed to prevent the worsening of disease phenotypes and sudden cardiac death (SCD). Despite the use of implantable cardioverter defibrillators (ICDs) there is no present therapy that would mitigate the loss in electrical signal and propagation by these fibrofatty barriers. Recent studies have shown the influence of forced vs. voluntary exercise in a variety of healthy and diseased mice; more specifically, that exercised mice show increased Connexin-43 (Cx43) expression levels. Fascinatingly, increased Cx43 expression ameliorated the abnormal electrical signal conduction in the myocardium of diseased mice. These findings point to a major translational pitfall in current therapeutics for ACM patients, who are advised to completely cease exercising and already demonstrate reduced Cx43 levels at the myocyte intercalated disc. Considering cardiac dysfunction in ACM arises from the loss of cardiomyocytes and electrical signal conduction abnormalities, an increase in Cx43 expression-promoted by low to moderate intensity exercise and/or gene therapy-could very well improve cardiac function in ACM patients.

Metabolic and metabolomics insights into dilated cardiomyopathy (DCM)

BACKGROUND

Dilated cardiomyopathy (DCM) is the most common form of heart muscle disease characterized by progressive dilatation and ventricular dysfunction. Metabolomics is an emerging and powerful discipline that provides a global information on the phenotype of mammalian systems via the study of endogenous and exogenous metabolites in cells, tissues and biofluids. These studies aid in the identification of biomarkers to prevent diseases in later life or help to early detect onset of diseases as well as aiding in the elucidation of disease mechanisms.

SUMMARY

Metabolomics provides a unique opportunity to discover biomarkers for DCM. This review demonstrates evidence of metabolite-based biomarkers useful for predicting, diagnosing and monitoring therapeutic interventions of DCM. Key metabolites identified as potential biomarkers for diagnosing DCM include acyl-carnitines, succinic acid, malate, methylhistidine, aspartate, methionine, phenylalanine. In terms of differentiating DCM from ICM, potential biomarkers including 1-pyrroline-2-carboxylate, norvaline, lysophosphatidylinositol (16:0/0:0), phosphatidylglycerol, fatty acid esters of hydroxy fatty acid, and phosphatidylcholine were identified. Acyl-carnitines, isoleucine and linoleic acid and tryptophan were the main biomarkers to monitor treatment response to DCM. Mapping metabolites to metabolic pathways revealed dysregulation of BCAA, glycolysis, tricarboxylic acid cycle and triacylglycerol and pentose phosphate metabolism which have therapeutic potential for DCM. This review shows several limitations including the use of small sample sizes, lack of interpretation of age and sex differences in most studies and the fact that studies have so far been limited to case-control study designs.

KEY MESSAGES

Metabolites have close proximity to disease phenotype. With recent advancements in metabolomics field, potential biomarkers for DCM have been identified based on studies using different biological and metabolomics technologies. However, multi-center studies with larger populations that will lead to validation of these identified biomarkers to enable their clinical translation and utilization are still needed.

Simulation Modeling of Reduced Glycosylation Effects on Potassium Channels of Mouse Cardiomyocytes

Dilated cardiomyopathy (DCM) is the third most common cause of heart failure and the primary reason for heart transplantation; upward of 70% of DCM cases are considered idiopathic. Our in-vitro experiments showed that reduced hybrid/complex N-glycosylation in mouse cardiomyocytes is linked with DCM. Further, we observed direct effects of reduced N-glycosylation on Kv gating. However, it is difficult to rigorously determine the effects of glycosylation on Kv activity, because there are multiple Kv isoforms in cardiomyocytes contributing to the cardiac excitation. Due to complex functions of Kv isoforms, only the sum of K+ currents (IKsum) can be recorded experimentally and decomposed later using exponential fitting to estimate component currents, such as IKto, IKslow, and IKss. However, such estimation cannot adequately describe glycosylation effects and Kv mechanisms. Here, we propose a framework of simulation modeling of Kv kinetics in mouse ventricular myocytes and model calibration using the in-vitro data under normal and reduced glycosylation conditions through ablation of the Mgat1 gene (i.e., Mgat1KO). Calibrated models facilitate the prediction of Kv characteristics at different voltages that are not directly observed in the in-vitro experiments. A model calibration procedure is developed based on the genetic algorithm. Experimental results show that, in the Mgat1KO group, both IKto and IKslow densities are shown to be significantly reduced and the rate of IKslow inactivation is much slower. The proposed approach has strong potential to couple simulation models with experimental data for gaining a better understanding of glycosylation effects on Kv kinetics.

Human Induced Pluripotent Stem Cell as a Disease Modeling and Drug Development Platform-A Cardiac Perspective

A comprehensive understanding of the pathophysiology and cellular responses to drugs in human heart disease is limited by species differences between humans and experimental animals. In addition, isolation of human cardiomyocytes (CMs) is complicated because cells obtained by biopsy do not proliferate to provide sufficient numbers of cells for preclinical studies in vitro. Interestingly, the discovery of human-induced pluripotent stem cell (hiPSC) has opened up the possibility of generating and studying heart disease in a culture dish. The combination of reprogramming and genome editing technologies to generate a broad spectrum of human heart diseases in vitro offers a great opportunity to elucidate gene function and mechanisms. However, to exploit the potential applications of hiPSC-derived-CMs for drug testing and studying adult-onset cardiac disease, a full functional characterization of maturation and metabolic traits is required. In this review, we focus on methods to reprogram somatic cells into hiPSC and the solutions for overcome immaturity of the hiPSC-derived-CMs to mimic the structure and physiological properties of the adult human CMs to accurately model disease and test drug safety. Finally, we discuss how to improve the culture, differentiation, and purification of CMs to obtain sufficient numbers of desired types of hiPSC-derived-CMs for disease modeling and drug development platform.

Cardiomyogenic Differentiation Potential of Human Dilated Myocardium-Derived Mesenchymal Stem/Stromal Cells: The Impact of HDAC Inhibitor SAHA and Biomimetic Matrices

Dilated cardiomyopathy (DCM) is the most common type of nonischemic cardiomyopathy characterized by left ventricular or biventricular dilation and impaired contraction leading to heart failure and even patients’ death. Therefore, it is important to search for new cardiac tissue regenerating tools. Human mesenchymal stem/stromal cells (hmMSCs) were isolated from post-surgery healthy and DCM myocardial biopsies and their differentiation to the cardiomyogenic direction has been investigated in vitro. Dilated hmMSCs were slightly bigger in size, grew slower, but had almost the same levels of MSC-typical surface markers as healthy hmMSCs. Histone deacetylase (HDAC) activity in dilated hmMSCs was 1.5-fold higher than in healthy ones, which was suppressed by class I and II HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) showing activation of cardiomyogenic differentiation-related genes alpha-cardiac actin (ACTC1) and cardiac troponin T (TNNT2). Both types of hmMSCs cultivated on collagen I hydrogels with hyaluronic acid (HA) or 2-methacryloyloxyethyl phosphorylcholine (MPC) and exposed to SAHA significantly downregulated focal adhesion kinase (PTK2) and activated ACTC1 and TNNT2. Longitudinal cultivation of dilated hmMSC also upregulated alpha-cardiac actin. Thus, HDAC inhibitor SAHA, in combination with collagen I-based hydrogels, can tilt the dilated myocardium hmMSC toward cardiomyogenic direction in vitro with further possible therapeutic application in vivo.

Decreased circulating follicular regulatory T cells in patients with dilated cardiomyopathy

Follicular regulatory T cells (Tfr) have critical functions in inflammatory and autoimmune disorders. The main purpose of the current work was to assess Tfr cell frequency in patients with dilated cardiomyopathy (DCM). Flow cytometry showed that, compared with normal controls, DCM cases showed markedly reduced Tfr cell rates and Tfr/Tfh ratios, but significantly increased follicular helper T cell (Tfh) rates. Correlation analysis showed that the Tfr rate in DCM patients was positively correlated with left ventricular ejection fraction (LVEF), and negatively correlated with N-terminal brain natriuretic peptide (NT-proBNP) levels. Lower Foxp3 and higher Bcl-6, ICOS, and PD-1 mRNA expression levels were found in patients with DCM. In addition, plasma interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-21 levels were significantly increased in DCM cases. Moreover, IgG and IgG3 levels were also elevated in individuals with DCM. Correlation analysis showed that the Tfr rate in DCM patients was negatively correlated with IgG and IgG3, while the Tfh rate was positively correlated with IgG and IgG3. Changes in circulating Tfr levels may have a critical immunomodulatory function in DCM and may become a new therapeutic target for DCM.

The Emerging Role of Epigenetics in Therapeutic Targeting of Cardiomyopathies

Cardiomyopathies (CMPs) are a heterogeneous group of myocardial diseases accountable for the majority of cases of heart failure (HF) and/or sudden cardiac death (SCD) worldwide. With the recent advances in genomics, the original classification of CMPs on the basis of morphological and functional criteria (dilated (DCM), hypertrophic (HCM), restrictive (RCM), and arrhythmogenic ventricular cardiomyopathy (AVC)) was further refined into genetic (inherited or familial) and acquired (non-inherited or secondary) forms. Despite substantial progress in the identification of novel CMP-associated genetic variations, as well as improved clinical recognition diagnoses, the functional consequences of these mutations and the exact details of the signaling pathways leading to hypertrophy, dilation, and/or contractile impairment remain elusive. To date, global research has mainly focused on the genetic factors underlying CMP pathogenesis. However, growing evidence shows that alterations in molecular mediators associated with the diagnosis of CMPs are not always correlated with genetic mutations, suggesting that additional mechanisms, such as epigenetics, may play a role in the onset or progression of CMPs. This review summarizes published findings of inherited CMPs with a specific focus on the potential role of epigenetic mechanisms in regulating these cardiac disorders.

Cardiomyopathies: An Overview

Background: Cardiomyopathies are a heterogeneous group of pathologies characterized by structural and functional alterations of the heart. Aims: The purpose of this narrative review is to focus on the most important cardiomyopathies and their epidemiology, diagnosis, and management. Methods: Clinical trials were identified by Pubmed until 30 March 2021. The search keywords were “cardiomyopathies, sudden cardiac arrest, dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy, arrhythmogenic cardiomyopathy (ARCV), takotsubo syndrome”. Results: Hypertrophic cardiomyopathy (HCM) is the most common primary cardiomyopathy, with a prevalence of 1:500 persons. Dilated cardiomyopathy (DCM) has a prevalence of 1:2500 and is the leading indication for heart transplantation. Restrictive cardiomyopathy (RCM) is the least common of the major cardiomyopathies, representing 2% to 5% of cases. Arrhythmogenic cardiomyopathy (ARCV) is a pathology characterized by the substitution of the myocardium by fibrofatty tissue. Takotsubo cardiomyopathy is defined as an abrupt onset of left ventricular dysfunction in response to severe emotional or physiologic stress. Conclusion: In particular, it has been reported that HCM is the most important cause of sudden death on the athletic field in the United States. It is needless to say how important it is to know which changes in the heart due to physical activity are normal, and when they are pathological.

Cardiac Autonomic Nervous System and Ventricular Arrhythmias: The Role of Radionuclide Molecular Imaging

Widely established compared to myocardial perfusion imaging, cardiac autonomous nervous system (CANS) assessment by radiopharmaceutical means is of potential use especially to arrhythmogenic diseases not correlated with anatomic or functional alterations revealed by classical imaging techniques. Molecular imaging of both pre- and postsynaptic functions of the autonomous nervous system is currently feasible, since single photon emission tomography (SPECT) and positron emission tomography (PET) have the ability to reveal the insights of molecular pathophysiology depicting both sympathetic and parasympathetic imbalance in discrete heart pathologies. This review provides not only a brief presentation of radiopharmaceuticals used for non-invasive CANS imaging in the case of ventricular arrhythmias, but also a current update on ventricular tachycardias, cardiomyopathies, Brugada and Long QT syndrome literature.

Insights into therapeutic targets and biomarkers using integrated multi-'omics' approaches for dilated and ischemic cardiomyopathies

At present, heart failure (HF) treatment only targets the symptoms based on the left ventricle dysfunction severity; however, the lack of systemic 'omics' studies and available biological data to uncover the heterogeneous underlying mechanisms signifies the need to shift the analytical paradigm towards network-centric and data mining approaches. This study, for the first time, aimed to investigate how bulk and single cell RNA-sequencing as well as the proteomics analysis of the human heart tissue can be integrated to uncover HF-specific networks and potential therapeutic targets or biomarkers. We also aimed to address the issue of dealing with a limited number of samples and to show how appropriate statistical models, enrichment with other datasets as well as machine learning-guided analysis can aid in such cases. Furthermore, we elucidated specific gene expression profiles using transcriptomic and mined data from public databases. This was achieved using the two-step machine learning algorithm to predict the likelihood of the therapeutic target or biomarker tractability based on a novel scoring system, which has also been introduced in this study. The described methodology could be very useful for the target or biomarker selection and evaluation during the pre-clinical therapeutics development stage as well as disease progression monitoring. In addition, the present study sheds new light into the complex aetiology of HF, differentiating between subtle changes in dilated cardiomyopathies (DCs) and ischemic cardiomyopathies (ICs) on the single cell, proteome and whole transcriptome level, demonstrating that HF might be dependent on the involvement of not only the cardiomyocytes but also on other cell populations. Identified tissue remodelling and inflammatory processes can be beneficial when selecting targeted pharmacological management for DCs or ICs, respectively.

Late-Gadolinium Enhancement Interface Area and Electrophysiological Simulations Predict Arrhythmic Events in Patients With Nonischemic Dilated Cardiomyopathy

OBJECTIVES

This study sought to investigate whether shape-based late gadolinium enhancement (LGE) metrics and simulations of re-entrant electrical activity are associated with arrhythmic events in patients with nonischemic dilated cardiomyopathy (NIDCM).

BACKGROUND

The presence of LGE predicts life-threatening ventricular arrhythmias in NIDCM; however, risk stratification remains imprecise. LGE shape and simulations of electrical activity may be able to provide additional prognostic information.

METHODS

Cardiac magnetic resonance (CMR)-LGE shape metrics were computed for a cohort of 156 patients with NIDCM and visible LGE and tested retrospectively for an association with an arrhythmic composite endpoint of sudden cardiac death and ventricular tachycardia. Computational models were created from images and used in conjunction with simulated stimulation protocols to assess the potential for re-entry induction in each patient's scar morphology. A mechanistic analysis of the simulations was carried out to explain the associations.

RESULTS

During a median follow-up of 1,611 (interquartile range: 881 to 2,341) days, 16 patients (10.3%) met the primary endpoint. In an inverse probability weighted Cox regression, the LGE-myocardial interface area (hazard ratio [HR]: 1.75; 95% confidence interval [CI]: 1.24 to 2.47; p = 0.001), number of simulated re-entries (HR: 1.40; 95% CI: 1.23 to 1.59; p < 0.01) and LGE volume (HR: 1.44; 95% CI: 1.07 to 1.94; p = 0.02) were associated with arrhythmic events. Computational modeling revealed repolarization heterogeneity and rate-dependent block of electrical wavefronts at the LGE-myocardial interface as putative arrhythmogenic mechanisms directly related to the LGE interface area.

CONCLUSIONS

The area of interface between scar and surviving myocardium, as well as simulated re-entrant activity, are associated with an elevated risk of major arrhythmic events in patients with NIDCM and LGE and represent novel risk predictors.

Leptin administration during lactation leads to different nutritional, biometric, hemodynamic, and cardiac outcomes in prepubertal and adult female Wistar rats

Literature reports that insults, such as hormonal disturbances, during critical periods of development may modulate organism physiology and metabolism favoring cardiovascular diseases (CVDs) later in life. Studies show that leptin administration during lactation leads to cardiovascular dysfunction in young and adult male Wistar rats. However, there are sex differences regarding CVD. Thus, the present work aimed to investigate neonatal leptin administration's consequences on different outcomes in female rats at prepubertal and adult age. Newborn Wistar female rats were divided into two groups, Leptin and Control, receiving daily subcutaneous injections of this adipokine (8 μg/100 g) or saline for the first 10 of 21 d of lactation. Nutritional, biometric, hemodynamic, and echocardiographic parameters, as well as maximal effort ergometer performance, were determined at postnatal days (PND) 30 and 150. Leptin group presented lower food intake (p = 0.0003) and higher feed efficiency (p = 0.0058) between PND 21 and 30. Differences concerning echocardiographic parameters revealed higher left ventricle internal diameter (LVID) in systole (p = 0.0051), as well as lower left ventricle ejection fraction (LVEF) (p = 0.0111) and fractional shortening (FS) (p = 0.0405) for this group at PND 30. Older rats treated with leptin during lactation presented only higher LVID in systole (p = 0.0270). Systolic blood pressure and maximum effort ergometer test performance was similar between groups at both ages. These data suggest that nutritional, biometric, and cardiac outcomes due to neonatal leptin administration in female rats are age-dependent.

H2S improves doxorubicin-induced myocardial fibrosis by inhibiting oxidative stress and apoptosis via Keap1-Nrf2

OBJECTIVE

We waimed to investigate whether H2S can relieve the myocardial fibrosis caused by doxorubicin through Keap1-Nrf2.

METHODS

Sprague-Dawley (SD) rats were randomly divided into four groups: normal control group (Control); DOX model group (DOX); H2S intervention model group (DOX+H2S); H2S control group (H2S). DOX and DOX+H2S group were injected with doxorubicin (3.0 mg/kg/time) intraperitoneally. Both of the Control group and H2S groups were given normal saline in equal volume, 2 weeks later, DOX+H2S and H2S group were controlled with NaHS (56 μmol/kg/d) through the abdominal cavity, while the Control and DOX group were injected with normal saline of the same dosage intraperitoneally.

RESULTS

Myocardial injury and myocardial cell apoptosis were significantly increased, the H2S content in myocardial tissue was remarkably down-regulated, the expression levels of MDA, Keap1, caspase-3, caspase-9, TNF-α, IL1β, MMPs and TIMP-1 in rat myocardial tissue was significantly up-regulated (P< 0.05), and the expression levels of GSH, NQO1, Bcl-2 were down-regulated compared with those of control group. The above results can be reversed by the DOX+H2S group. There is no statistically significant difference between the Control group and the H2S control group.

CONCLUSIONS

These results suggest that H2S can improve DOX-induced myocardial fibrosis in rats, and the keap1/Nrf2 signaling pathway, oxidative stress, inflammation, and apoptosis may be involved in the mechanism.

Genomic analysis of circular RNAs in heart

BACKGROUND

Heart failure is a leading cause of human morbidity and mortality. Circular RNAs (circRNAs) are a newly discovered class of RNA that have been found to have important physiological and pathological roles. In the current study, we de novo analyzed existing whole transcriptome data from 5 normal and 5 dilated cardiomyopathy (DCM) human heart samples and compared the results with circRNAs that have been previously reported in human, mouse and rat hearts.

RESULTS

Our analysis identifies a list of cardiac circRNAs that are reliably detected in multiple studies. We have also defined the top 30 most abundant circRNAs in healthy human hearts which include some with previously unrecognized cardiac roles such as circHIPK3_11 and circTULP4_1. We further found that many circRNAs are dysregulated in DCM, particularly transcripts originating from DCM-related gene loci, such as TTN and RYR2. In addition, we predict the potential of cardiac circRNAs to sponge miRNAs that have reported roles in heart disease. We found that circALMS1_6 has the highest potential to bind miR-133, a microRNA that can regulate cardiac remodeling. Interestingly, we detected a novel class of circRNAs, referred to as read-though (rt)-circRNAs which are produced from exons of two different neighboring genes. Specifically, rt-circRNAs from SCAF8 and TIAM2 were observed to be dysregulated in DCM and these rt-circRNAs have the potential to sponge multiple heart disease-related miRNAs.

CONCLUSIONS

In summary, this study provides a valuable resource for exploring the function of circRNAs in human heart disease and establishes a functional paradigm for identifying novel circRNAs in other tissues.

Epinephrine soaked tampons induced transient acute dilated cardiomyopathy during FESS procedure

Background

Epinephrine, in all modes of use, may pose a wide range of cardiotoxic events, ranging from sinus tachycardia to heart failure, life threatening arrhythmias, and even death. Because of daily and extensive use of epinephrine, these unusual and rare events tend to be forgotten by physicians. We present a case of dilated cardiomyopathy that developed following routine use of epinephrine-impregnated tampons during function endoscopic sinus (FESS) surgery.

Case presentation

A healthy, 24-year-old man with no family history of heart disease has undergone elective surgery under general anesthesia to repair the paranasal sinuses using endoscopic approach. During surgery, soon after being treated with 1: 1000 diluted epinephrine-soaked tampons, an hypertensive crisis was noticed followed by pulseless electrical activity. An extensive examination led to the diagnosis of non-ischemic dilated cardiomyopathy. After several days of heart failure medical therapy, complete resolution of all structural and functional changes was achieved.

Conclusion

In our case, we present an unusual and rare event of acute dilated cardiomyopathy following the use of epinephrine-soaked tampons during elective FESS surgery. A prompt response was observed after several days of heart failure treatment. Awareness of the epinephrine cardiotoxic potential even in the form of soaked tampons is essential for proper diagnosis and prompt treatment.

Therapeutic potential of cPLA2 inhibitor to counteract dilated-cardiomyopathy in cholesterol-treated H9C2 cardiomyocyte and MUNO rat

BACKGROUND AND PURPOSE

The pathogenesis of cardiomyopathy in metabolically unhealthy obesity (MUO) has been well studied. However, the pathogenesis of cardiomyopathy typically associated with high cholesterol levels in metabolically unhealthy nonobesity (MUNO) remains unclear. We investigated whether cholesterol-generated LysoPCs contribute to cardiomyopathy and the role of cytosolic phospholipase A2 (cPLA2) inhibitor in cholesterol-induced MUNO.

EXPERIMENTAL APPROACH

Cholesterol diet was performed in Sprague-Dawley rats that were fed either regular chow (C), or high cholesterol chow (HC), or HC diet with 10 % fructose in drinking water (HCF) for 12 weeks. LysoPCs levels were subsequently measured in rats and in MUNO human patients. The effects of cholesterol-mediated LysoPCs on cardiac injury, and the action of cPLA2 inhibitor, AACOCF3, were further assessed in H9C2 cardiomyocytes.

KEY RESULTS

HC and HCF rats fed cholesterol diets demonstrated a MUNO-phenotype and cholesterol-induced dilated cardiomyopathy (DCM). Upregulated levels of LysoPCs were found in rat myocardium and the plasma in MUNO human patients. Further testing in H9C2 cardiomyocytes revealed that cholesterol-induced atrophy and death of cardiomyocytes was due to mitochondrial dysfunction and conditions favoring DCM (i.e. reduced mRNA expression of ANF, BNP, DSP, and atrogin-1), and that AACOCF3 counteracted the cholesterol-induced DCM phenotype.

CONCLUSION AND IMPLICATIONS

Cholesterol-induced MUNO-DCM phenotype was counteracted by cPLA2 inhibitor, which is potentially useful for the treatment of LysoPCs-associated DCM in MUNO.

Homozygous G650del nexilin variant causes cardiomyopathy in mice

Nexilin (NEXN) was recently identified as a component of the junctional membrane complex required for development and maintenance of cardiac T-tubules. Loss of Nexn in mice leads to a rapidly progressive dilated cardiomyopathy (DCM) and premature death. A 3 bp deletion (1948-1950del) leading to loss of the glycine in position 650 (G650del) is classified as a variant of uncertain significance in humans and may function as an intermediate risk allele. To determine the effect of the G650del variant on cardiac structure and function, we generated a G645del-knockin (G645del is equivalent to human G650del) mouse model. Homozygous G645del mice express about 30% of the Nexn expressed by WT controls and exhibited a progressive DCM characterized by reduced T-tubule formation, with disorganization of the transverse-axial tubular system. On the other hand, heterozygous Nexn global KO mice and genetically engineered mice encoding a truncated Nexn missing the first N-terminal actin-binding domain exhibited normal cardiac function, despite expressing only 50% and 20% of the Nexn, respectively, expressed by WT controls, suggesting that not only quantity but also quality of Nexn is necessary for a proper function. These findings demonstrated that Nexn G645 is crucial for Nexn's function in tubular system organization and normal cardiac function.

Prognostic value of late gadolinium enhancement in cardiac MRI of non-ischemic dilated cardiomyopathy patients

Background

The role of late gadolinium enhancement (LGE) in cardiac MRI (CMR) as prognostic marker in non-ischemic dilated cardiomyopathy (NIDCM) is evolving.

Objective

To study the effect of LGE in the prognosis of NIDCM patients.

Methods

112 consecutive NIDCM patients, who underwent CMR, were prospectively followed up for 745 ± 320 days. Primary end point was occurrence of MACE {composite of all-cause mortality, resuscitated cardiac arrest, sustained ventricular tachycardia (VT)/appropriate ICD shock, heart failure (HF) hospitalization}.

Results

LGE was present in 44 out of 112 patients (39%). The primary end point (MACE) was significantly higher in LGE + ve group compared to the LGE –ve group (72.7% vs. 29.4%; p < 0.0001). Similarly, cardiac mortality (9.1% vs 2.9%; p < 0.049), VT (13.6% vs. 2.9%; p < 0.031), HF hospitalization (63.6% vs. 30.9%; p < 0.001) were significantly more in LGE + ve group. In univariate model, LGE demonstrated the strongest association with MACE (Hazard ratio [HR] = 2.96 [95% CI 1.685 to 5.201; p < 0.0001). LGE extent of >14% of LV predicted MACE with 90.6% sensitivity and 86% specificity. HR of LGE extent >14% of LV for MACE is 6.12; p < 0.01. LGE was associated with MACE irrespective of its location, pattern or distribution. Multivariate model showed LGE and its extent >14% of LV volume were strongest predictor of MACE.

Conclusion

LGE and its extent >14% predicts adverse cardiac events in NIDCM irrespective of LVEF and LGE location, pattern or distribution. This study emphasises the role of CMR in risk stratification of NIDCM patients and guiding therapy.

CFTR deficiency causes cardiac dysplasia during zebrafish embryogenesis and is associated with dilated cardiomyopathy

Mutations in the CFTR gene cause cystic fibrosis (CF) with myocardial dysfunction. However, it remains unknown whether CF-related heart disease is a secondary effect of pulmonary disease, or an intrinsic primary defect in the heart. Here, we used zebrafish, which lack lung tissue, to investigate the role of CFTR in cardiogenesis. Our findings demonstrated that the loss of CFTR impairs cardiac development from the cardiac progenitor stage, resulting in cardiac looping defects, a dilated atrium, pericardial edema, and a decrease in heart rate. Furthermore, we found that cardiac development was perturbed in wild-type embryos treated with a gating-specific CFTR channel inhibitor, CFTRinh-172, at the blastula stage of development, but not at later stages. Gene expression analysis of blastulas indicated that transcript levels, including mRNAs associated with cardiovascular diseases, were significantly altered in embryos derived from cftr mutants relative to controls. To evaluate the role of CFTR in human heart failure, we performed a genetic association study on individuals with dilated cardiomyopathy and found that the I556V mutation in CFTR, which causes a channel defect, was associated with the disease. Similar to other well-studied channel-defective CFTR mutants, CFTR I556V mRNA failed to restore cardiac dysplasia in mutant embryos. The present study revealed an important role for the CFTR ion channel in regulating cardiac development during early embryogenesis, supporting the hypothesis that CF-related heart disease results from an intrinsic primary defect in the heart.

Potential Clinical Implications of miR-1 and miR-21 in Heart Disease and Cardioprotection

The interest in non-coding RNAs, which started more than a decade ago, has still not weakened. A wealth of experimental and clinical studies has suggested the potential of non-coding RNAs, especially the short-sized microRNAs (miRs), to be used as the new generation of therapeutic targets and biomarkers of cardiovascular disease, an ever-growing public health issue in the modern world. Among the hundreds of miRs characterized so far, microRNA-1 (miR-1) and microRNA-21 (miR-21) have received some attention and have been associated with cardiac injury and cardioprotection. In this review article, we summarize the current knowledge of the function of these two miRs in the heart, their association with cardiac injury, and their potential cardioprotective roles and biomarker value. While this field has already been extensively studied, much remains to be done before research findings can be translated into clinical application for patient’s benefit.

Arrhythmogenic Left Ventricular Cardiomyopathy: A Clinical and CMR Study

The clinical features, CMR characteristics and outcomes of arrhythmogenic left ventricular cardiomyopathy (ALVC), which is a very rare nonischemic cardiomyopathy, are currently not well studied. The purpose of the study is to investigate the clinical and cardiovascular magnetic resonance (CMR) imaging characteristics of arrhythmogenic left ventricular cardiomyopathy (ALVC). Fifty-three consecutive patients with ALVC were divided into two groups: ALVC patients without right ventricular (RV) involvement (n = 36, group 1) and those with RV involvement (n = 17, group 2). Clinical symptoms, cardiac electrophysiological findings, and CMR parameters (morphology, ventricular function, and myocardial fibrosis and fatty infiltration) were evaluated in both groups. The two groups showed no significant difference in age, gender, or presenting symptoms (P > 0.05). Right bundle branch block ventricular arrhythmia was less common in patients without RV involvement (50.0% vs.64.7%, P = 0.031). There were no significant differences in left ventricular function between the two groups, however right ventricular ejection fraction was significantly lower in group 2 (40.1 ± 4.0% vs. 48.7 ± 3.9%, P < 0.001). Inverse correlations of left ventricular ejection fraction with fat volume (r = −0.883, p = 0.001), late gadolinium enhancement (LGE) volume (r = −0.892, 0.013), ratio of fat/LGE (r = −0.848, p < 0.001), indexed left ventricular end diastolic volume (r = −0.877, p < 0.001) and indexed left ventricular end systolic volume (r = −0.943, p < 0.001) were all significant. ALVC is a rare disease with fibro-fatty replacement predominantly in the left ventricle, impaired left ventricular systolic function, and ventricular arrhythmias originating from the left ventricle. ALVC with right ventricular involvement may have a worse prognosis.

Advances in the role and mechanism of BAG3 in dilated cardiomyopathy

The B cell lymphoma 2-associated anthanogene (BAG3) is an anti-apoptotic co-chaperone protein. Previous reports suggest that mutations in BAG3 are associated with dilated cardiomyopathy. This review aims to summarize the current understanding of the relationship between BAG3 mutations and dilated cardiomyopathy, primarily focusing on the role and protective mechanism of BAG3 in cardiomyocytes from individuals with dilated cardiomyopathy. The results of published studies show that BAG3 is critically important for reducing cardiomyocyte apoptosis, maintaining protein homeostasis, regulating mitochondrial stability, modulating myocardial contraction, and reducing cardiac arrhythmia, which suggests an indispensable protective mechanism of BAG3 in dilated cardiomyopathy. The significant role of BAG3 in protecting cardiomyocytes provides a new direction for the diagnosis and treatment of dilated cardiomyopathy. However, further research is required to explore the molecular mechanisms that regulate BAG3 expression, to identify a novel therapy for patients with dilated cardiomyopathy.

Advances in MRI Applications to Diagnose and Manage Cardiomyopathies

PURPOSE OF REVIEW

The prevalence of heart failure continues to rise, and imaging characterization of the cardiomyopathic process is important for identifying myocardial disease, initiating appropriate treatment, and improving outcomes. We aimed to summarize recent advances in cardiac magnetic resonance imaging (CMR) applications for the diagnosis, characterization, and implications on management of various cardiomyopathies.

RECENT FINDINGS

Parametric mapping by CMR has emerged as an important advancement in quantification of myocardial fibrosis, increased extracellular space, and myocardial edema. In addition, improved assessment of myocardial function with myocardial strain assessment may provide early identification of patients at risk and determining responsiveness to therapeutic interventions. Novel MRI techniques and the advent of artificial intelligence may help to uncover important mechanistic insights into the cardiomyopathic process. Innovative CMR techniques continue to evolve, and it will be of interest to determine how these advances can be incorporated into clinical practice to improve diagnosis, treatment, and management of patients with cardiomyopathies.

Dilated cardiomyopathy: from epidemiologic to genetic phenotypes: A translational review of current literature

Dilated cardiomyopathy (DCM) is characterized by left ventricular dilatation and, consecutively, contractile dysfunction. The causes of DCM are heterogeneous. DCM often results from myocarditis, exposure to alcohol, drugs or other toxins and metabolic or endocrine disturbances. In about 35% of patients, genetic mutations can be identified that usually involve genes responsible for cytoskeletal, sarcomere and nuclear envelope proteins. Due to its heterogeneity, a detailed diagnostic work-up is necessary to identify the specific underlying cause and exclude other conditions with phenotype overlap. Patients with DCM show typical systolic heart failure symptoms, but, with progress of the disease, diastolic dysfunction is present as well. Depending on the underlying pathology, DCM patients also become apparent through arrhythmias, thromboembolic events or cardiogenic shock. Disease progression and prognosis are mostly driven by disease severity and reverse remodelling within the heart. The worst prognosis is seen in patients with lowest ejection fractions or severe diastolic dysfunction, leading to terminal heart failure with subsequent need for left ventricular assist device implantation or heart transplantation. Guideline-based heart failure medication and device therapy reduces the frequency of heart failure hospitalizations and improves survival.

Variants in NKX2-5 and FLNC Cause Dilated Cardiomyopathy and Sudden Cardiac Death

BACKGROUND

Dilated cardiomyopathy (DCM) is an important cause of heart failure. Variants in >50 genes have been reported to cause DCM, but causative variants have been found in less than half of familial cases. Variants causing DCM in Iceland have not been reported before.

METHODS

We performed a genome-wide association study on DCM based on whole genome sequencing. We tested the association of 32.5 million sequence variants in 424 cases and 337 689 population controls in Iceland.

RESULTS

We identified 2 DCM variants in established cardiomyopathy genes, a missense variant p.Phe145Leu in NKX2-5 carried by 1 in 7100 Icelanders ( P=7.0×10^-12) and a frameshift variant p.Phe1626Serfs*40 in FLNC carried by 1 in 3600 Icelanders ( P=2.1×10^-10). Both variants associate with heart failure and sudden cardiac death. Additionally, p.Phe145Leu in NKX2-5 associates with high degree atrioventricular block and atrial septal defect ( P<1.4×10^-4). The penetrance of serious heart disease among carriers of the NKX2-5 variant is high and higher than that of the FLNC variant.

CONCLUSIONS

Two rare variants in NKX2-5 and FLNC, carried by 1 in 2400 Icelanders, cause familial DCM in Iceland. These genes have recently been associated with DCM. Given the serious consequences of these variants, we suggest screening for them in individuals with DCM and their family members, with subsequent monitoring of carriers, offering early intervention.

Localized Structural Alterations Underlying a Subset of Unexplained Sudden Cardiac Death

Supplemental Digital Content is available in the text.

Background:

Sudden cardiac death because of ventricular fibrillation (VF) is commonly unexplained in younger victims. Detailed electrophysiological mapping in such patients has not been reported.

Methods:

We evaluated 24 patients (29±13 years) who survived idiopathic VF. First, we used multielectrode body surface recordings to identify the drivers maintaining VF. Then, we analyzed electrograms in the driver regions using endocardial and epicardial catheter mapping during sinus rhythm. Established electrogram criteria were used to identify the presence of structural alterations.

Results:

VF occurred spontaneously in 3 patients and was induced in 16, whereas VF was noninducible in 5. VF mapping demonstrated reentrant and focal activities (87% versus 13%, respectively) in all. The activities were dominant in one ventricle in 9 patients, whereas they had biventricular distribution in others. During sinus rhythm areas of abnormal electrograms were identified in 15/24 patients (62.5%) revealing localized structural alterations: in the right ventricle in 11, the left ventricle in 1, and both in 3. They covered a limited surface (13±6 cm²) representing 5±3% of the total surface and were recorded predominantly on the epicardium. Seventy-six percent of these areas were colocated with VF drivers (P<0.001). In the 9 patients without structural alteration, we observed a high incidence of Purkinje triggers (7/9 versus 4/15, P=0.033). Catheter ablation resulted in arrhythmia-free outcome in 15/18 patients at 17±11 months follow-up.

Conclusions:

This study shows that localized structural alterations underlie a significant subset of previously unexplained sudden cardiac death. In the other subset, Purkinje electrical pathology seems as a dominant mechanism.

Plasma osteopontin levels, but not its myocardial expression, reflect heart failure severity in recently diagnosed dilated cardiomyopathy

BACKGROUND

Elevated levels of the extracellular matrix glycoprotein osteopontin (OPN) may be detected in both myocardium and plasma under various pathological conditions affecting the heart. Several studies demonstrated increased plasma OPN levels in patients with heart failure due to dilated cardiomyopathy (DCM), while other studies showed high OPN expression levels in the myocardium of such patients. However, very little is known about OPN levels in both plasma and myocardium of the same individual with DCM. Therefore, we aimed to compare plasma OPN levels and levels of myocardial OPN expression in patients with recent-onset DCM (Ro-DCM).

METHODS

We examined plasma OPN as well as creatinine, C‑reactive protein (CRP), brain natriuretic peptide (BNP), and troponin I levels in 25 patients with Ro-DCM. Furthermore, all subjects underwent transthoracic echocardiography, selective coronary angiography, and endomyocardial biopsy (EMB) for the assessment of myocardial OPN expression.

RESULTS

No significant correlation between myocardial OPN expression and clinical, biochemical, or echocardiographic parameters was found. In log transformation analysis, plasma OPN levels correlated significantly with BNP levels (r = 0.46, p = 0.031), with CRP levels (r = 0.52, p = 0.015), and with early diastolic mitral annular velocity (r = -0.57, p = 0.009). There was a borderline association between the plasma OPN log value and New York Heart Association class (p = 0.053).

CONCLUSION

Plasma OPN levels reflect heart failure severity in patients with Ro-DCM. Myocardial OPN expression is not associated with either plasma OPN levels or markers of heart failure in these individuals.

Reduced hybrid/complex N-glycosylation disrupts cardiac electrical signaling and calcium handling in a model of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is the third most common cause of heart failure, with ~70% of DCM cases considered idiopathic. We showed recently, through genetic ablation of the MGAT1 gene, which encodes an essential glycosyltransferase (GlcNAcT1), that prevention of cardiomyocyte hybrid/complex N-glycosylation was sufficient to cause DCM that led to heart failure and early death. Our findings are consistent with increasing evidence suggesting a link between aberrant glycosylation and heart diseases of acquired and congenital etiologies. However, the mechanisms by which changes in glycosylation contribute to disease onset and progression remain largely unknown. Activity and gating of voltage-gated Na⁺ and K⁺ channels (Na_v and K_v respectively) play pivotal roles in the initiation, shaping and conduction of cardiomyocyte action potentials (APs) and aberrant channel activity was shown to contribute to cardiac disease. We and others showed that glycosylation can impact Na_v and K_v function; therefore, here, we investigated the effects of reduced cardiomyocyte hybrid/complex N-glycosylation on channel activity to investigate whether chronic aberrant channel function can contribute to DCM. Ventricular cardiomyocytes from MGAT1 deficient (MGAT1KO) mice display prolonged APs and pacing-induced aberrant early re-activation that can be attributed to, at least in part, a significant reduction in K_v expression and activity that worsens over time suggesting heart disease-related remodeling. MGAT1KO Na_v demonstrate no change in expression or maximal conductance but show depolarizing shifts in voltage-dependent gating. Together, the changes in MGAT1KO Na_v and K_v function likely contribute to observed anomalous electrocardiograms and Ca²⁺ handling. These findings provide insight into mechanisms by which altered glycosylation contributes to DCM through changes in Na_v and K_v activity that impact conduction, Ca²⁺ handling and contraction. The MGAT1KO can also serve as a useful model to study the effects of aberrant electrical signaling on cardiac function and the remodeling events that can occur with heart disease progression.

The Many Faces of Heart Failure

Heart failure is a heterogeneous clinical syndrome stemming from cardiac overload and injury that leads to considerable morbidity and mortality. This review highlights the many faces of heart failure, a major and growing public health problem, including its causes, classification, underlying pathophysiology, and variable progression. An individualized, patient-centered treatment approach that focuses on guideline-directed pharmacologic and device therapies is required for optimal management of this complex syndrome.

Male Patients With Dilated Cardiomyopathy Exhibiting a Higher Heart Rate Acceleration Capacity or a Lower Deceleration Capacity Are at Higher Risk of Cardiac Death

The effects of dilated cardiomyopathy (DCM) on cardiac autonomic regulation and electrophysiology, and the consequences of such changes, remain unclear. We evaluated the associations between heart rate acceleration capacity (AC) and deceleration capacity (DC), heart structural and functional changes, and cardiac death in 202 healthy controls and 100 DCM patients. The DC was lower and the AC was higher in DCM patients (both males and females). Multivariable, linear, logistic regression analyses revealed that in males, age was positively associated with AC in healthy controls (N = 85); the left atrial diameter (LAD) was positively and the left ventricular ejection fraction (LVEF) was negatively associated with AC in DCM patients (N = 65); age was negatively associated with DC in healthy controls (N = 85); and the LAD was negatively and the LVEF was positively associated with DC in DCM patients (N = 65). In females, only age was associated with either AC or DC in healthy controls (N = 117). Kaplan–Meier analysis revealed that male DCM patients with greater LADs (≥46.5 mm) (long-rank chi-squared value = 11.1, P = 0.001), an elevated AC (≥-4.75 ms) (log-rank chi-squared value = 6.8, P = 0.009), and a lower DC (≤4.72 ms) (log-rank chi-squared value = 9.1, P = 0.003) were at higher risk of cardiac death within 60 months of follow-up. In conclusion, in males, DCM significantly affected both the AC and DC; a higher AC or a lower DC increased the risk of cardiac death.

Circular RNAs as Potential Theranostics in the Cardiovascular System

Cardiovascular diseases (CVDs) represent the largest contributor to mortality worldwide. Identification of novel therapeutic targets and biomarkers for CVDs is urgently needed. Circular RNAs (circRNAs) are endogenous, abundant, and stable non-coding RNAs formed by back-splicing events. Their role as regulators of gene expression has been increasingly reported. Notably, circRNAs mediate essential physiological and pathological processes in the cardiovascular system. Our first aim, therefore, is to summarize recent advances in the role of circRNAs in cardiac development as well as in pathogenesis of various CVDs. Because circRNAs are stable in circulation and their dynamic changes may reflect different disease stages, they are considered ideal biomarkers. Therefore, our second aim is to review studies that have identified circulating circRNAs as biomarkers for CVDs. Finally, we discuss the shortage of functional studies and the limitations of available clinical studies and provide future perspectives.

A novel heterozygous variant p.(Trp538Arg) of SYNM is identified by whole-exome sequencing in a Chinese family with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a relatively frequent myocardial disease that may lead to heart failure, syncope, and sudden cardiac death. Genetic factors play important roles in the etiology of the disease. To date, at least 50 genes have been identified in patients with DCM, among them, only three mutations have been reported in Synemin (SYNM) gene. In this study, we investigate a Chinese family of three generations with four patients with DCM. Employing whole-exome sequencing (WES) and bioinformatics strategies, a novel heterozygous missense mutation p.(Trp538Arg) of SYNM was identified and cosegregated with the affected family members. The missense mutation locates in the C-terminal domain of SYNM and leads to a substitution of tryptophan by arginine and may cause the structure change of synemin protein. In conclusion, we employed WES to detect the mutations of DCM patients and identified a novel likely pathogenic mutation in SYNM gene. Our study not only expands the spectrum of SYNM mutations, it further confirms that mutations in SYMN may underlie nonfamilial DCM, and offers genetic testing information to additional DCM patients.

Reduced myocyte complex N-glycosylation causes dilated cardiomyopathy

Protein glycosylation is an essential posttranslational modification that affects a myriad of physiologic processes. Humans with genetic defects in glycosylation, which result in truncated glycans, often present with significant cardiac deficits. Acquired heart diseases and their associated risk factors were also linked to aberrant glycosylation, highlighting its importance in human cardiac disease. In both cases, the link between causation and corollary remains enigmatic. The glycosyltransferase gene, mannosyl (α-1,3-)-glycoprotein β-1,2- N-acetylglucosaminyltransferase (Mgat1), whose product, N-acetylglucosaminyltransferase 1 (GlcNAcT1) is necessary for the formation of hybrid and complex N-glycan structures in the medial Golgi, was shown to be at reduced levels in human end-stage cardiomyopathy, thus making Mgat1 an attractive target for investigating the role of hybrid/complex N-glycosylation in cardiac pathogenesis. Here, we created a cardiomyocyte-specific Mgat1 knockout (KO) mouse to establish a model useful in exploring the relationship between hybrid/complex N-glycosylation and cardiac function and disease. Biochemical and glycomic analyses showed that Mgat1KO cardiomyocytes produce predominately truncated N-glycan structures. All Mgat1KO mice died significantly younger than control mice and demonstrated chamber dilation and systolic dysfunction resembling human dilated cardiomyopathy (DCM). Data also indicate that a cardiomyocyte L-type voltage-gated Ca²⁺ channel (Ca_v) subunit (α2δ1) is a GlcNAcT1 target, and Mgat1KO Ca_v activity is shifted to more-depolarized membrane potentials. Consistently, Mgat1KO cardiomyocyte Ca²⁺ handling is altered and contraction is dyssynchronous compared with controls. The data demonstrate that reduced hybrid/complex N-glycosylation contributes to aberrant cardiac function at whole-heart and myocyte levels drawing a direct link between altered glycosylation and heart disease. Thus, the Mgat1KO provides a model for investigating the relationship between systemic reductions in glycosylation and cardiac disease, showing that clinically relevant changes in cardiomyocyte hybrid/complex N-glycosylation are sufficient to cause DCM and early death.-Ednie, A. R., Deng, W., Yip, K.-P., Bennett, E. S. Reduced myocyte complex N-glycosylation causes dilated cardiomyopathy.

Chronic Ethanol Administration Prevents Compensatory Cardiac Hypertrophy in Pressure Overload

BACKGROUND

Alcohol is among the most commonly abused drugs worldwide and affects many organ systems, including the heart. Alcoholic cardiomyopathy is characterized by a dilated cardiac phenotype with extensive hypertrophy and extracellular matrix (ECM) remodeling. We have previously shown that chronic ethanol (EtOH) administration accelerates the progression to heart failure in a rat model of volume overload. However, the mechanism by which this decompensation occurs is unknown. For this study, we hypothesized that chronic EtOH administration would prevent compensatory hypertrophy and cardiac remodeling in a rodent model of pressure overload (PO).

METHODS

Abdominal aortic constriction was used to create PO in 8-week-old male Wistar rats. Alcohol administration was performed via chronic intermittent EtOH vapor inhalation for 2 weeks prior to surgery and for the duration of the 8-week study. Echocardiography measurements were taken to assess ventricular functional and structural changes.

RESULTS

PO increased posterior wall thickness and the hypertrophic markers, atrial and B-type natriuretic peptides (ANP and BNP). With the added stressor of EtOH, wall thickness, ANP, and BNP decreased in PO animals. The combination of PO and EtOH resulted in increased wall stress compared to PO alone. PO also caused increased expression of collagen I and III, whereas EtOH alone only increased collagen III. The combined stresses of PO and EtOH led to an increase in collagen I expression, but collagen III did not change, resulting in an increased collagen I/III ratio in the PO rats treated with EtOH. Lastly, Notch1 expression was significantly increased only in the PO rats treated with EtOH.

CONCLUSIONS

Our data indicate that chronic EtOH may limit the cardiac hypertrophy induced by PO which may be associated with a Notch1 mechanism, resulting in increased wall stress and altered ECM profile.

Coronary Microcirculatory Dysfunction in Human Cardiomyopathies: A Pathologic and Pathophysiologic Review

Cardiomyopathies are a heterogeneous group of diseases of the myocardium. The term cardiomyopathy involves a wide range of pathogenic mechanisms that affect the structural and functional states of cardiomyocytes, extravascular tissues, and coronary vasculature, including both epicardial coronary arteries and the microcirculation. In the developed phase, cardiomyopathies present with various clinical symptoms: dyspnea, chest pain, palpitations, swelling of the extremities, arrhythmias, and sudden cardiac death. Due to the heterogeneity of cardiomyopathic patterns and symptoms, their diagnosis and therapies are great challenges. Despite extensive research, the relation between the structural and functional abnormalities of the myocardium and the coronary circulation are still not well understood in the various forms of cardiomyopathy. The main pathological characteristics of cardiomyopathies and the coronary microcirculation develop in a progressive manner due to (1) genetic-immunologic-systemic factors; (2) comorbidities with endothelial, myogenic, metabolic, and inflammatory changes; (3) aging-induced arteriosclerosis; and (4) myocardial fibrosis. The aim of this review is to summarize the most important common pathological features and/or adaptations of the coronary microcirculation in various types of cardiomyopathies and to integrate the present understanding of the underlying pathophysiological mechanisms responsible for the development of various types of cardiomyopathies. Although microvascular dysfunction is present and contributes to cardiac dysfunction and the potential outcome of disease, the current therapeutic approaches are not specific for the given types of cardiomyopathy.